Effective electrostatic potential surface and aromatic affinity as quantitative guide for deep extraction denitrification from aromatic-rich oils

Abstract

High polar and reactive nitrogen-containing compounds greatly hinder the application of slurry oil (SO) in carbon-based materials. Compared with the hydrodenitrification process, the extraction process avoids aromatic saturation. However, pure experiments could not effectively screen extractants because of the structural similarity of polycyclic aromatic hydrocarbon (PAH) and nitrogen-containing PAH (NC-PAH). This work focused on searching for deep eutectic solvents (DESs) through sequential theoretical screening methods. The contradiction between denitrification efficiency (DN) and PAH loss (PL) could be weakened. Firstly, column chromatography, GC–MS, etc. were used to determine the molecular structure. The σ-profile, which performs the hydrogen bond acceptors (HBAs) property of molecules, was employed to crudely screen HBAs. Then, the interaction mechanism was obtained by multiple wave function analyses. An index named effective electrostatic potential (ESP) surface area, coined EES, was defined as the area of the region that apparently affected the interaction to predict DN. Additionally, the interaction energy (IE) of the cation of HBAs and non-basic PAH (nNC-PAH) was used to assess aromatic affinity and PL. The IE of HBAs and nNC-PAH linearly increased with EES, R2 = 0.9558. Meanwhile, DN was positively and linearly correlated with IE. Moreover, PL decreased slightly, then sharply, with the increase in aromatic affinity. The DN could reach about 65.1%, and the PL was limited to 3.8% after searching for high DN by EES and excluding high PL by aromatic affinity. These denitrification performances are crucially beneficial to the further preparation of carbon materials.